Fibrillation



B. SKINNER FIBRILLATION Jan. 20, 1970 2 Sheets--Sheet 1 Original Filed July 5, 1966 uvvswron BRADLEY SKI NNER A 7' TORNEYS Jan. 20, 1970 3,490,663

B. SKINNER 0 O 116. Filed July 5, 1966 A mmmmmmmmmm mm V/////A V/////////// 3O 3O 3O United States Patent 3,490,663 FIBRILLATION Bradley Skinner, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Original application July 5, 1966, Ser. No. 562,841, now Patent No. 3,416,714, dated Dec. 17, 1968. Divided and this application May 3, 1968, Ser. No. 726,430 Int. Cl. 1326f 3/00; B65l1 35/00; D02g 3/00 U.S. Cl. 225-93 4 Claims ABSTRACT OF THE DISCLOSURE An oriented film is fibrillated with a fluid stream by impinging the stream on a localized area of the film, gradually moving the stream across said film.

This is a division of application Ser. No. 562,841, filed July 5, 1'966,'now Patent No. 3,416,714.

This invention relates to a method and apparatus for making nonwoven fabric from a fibrillated plastic film or for fibrillating a plastic film.

Heretofore oriented plastic films have been fibrillated, i.e., split into a unitary, integral, coherent network of longitudinally extending fibers integrally joined to one another along the lengths thereof by smaller diameter and shorter fibers, by stretching, rubbing, piercing, beating, and the like. Various methods of fibrillating oriented film and opening out the fibrillated film so that the longitudinal fibers are substantially laterally spaced from one another to an extent greater than in the as fibrillated condition are fully disclosed in U.S. Patent 3,003,- 304, the disclosure of which is incorporated herein by reference. In general, many of the processes employed heretofore have randomly applied fibrillation energy to the film. In the case of some of these processes minute areas of the film may be left relatively untouched and therefore not fibrillated.

According to this invention an extremely uniform application of fibrillation or opening out energy across substantially the entire width and length of the film to be fibrillated or fibrillated film to be opened out can be obtained by impinging a high energy fluid stream on a first small, localized area of the film, this first area being substantially smaller than the width or length of the film, and then gradually moving the fluid stream or a counterpart thereof across a succession of similar small, localized areas until the fluid stream has traversedsubstantially the entire length and width of the film.

Accordingly, the apparatus of this invention employs a pillow block having an elongate fluid emission means such as a groove extending across at least a part of the width thereof, the width of the portion of the pillow block that contains emission means being approximately the width of the film to be fibrillated or expanded into nonwoven fabric. A header means is operatively connected to the emission means through the pillow block or otherwise in at least one place for supplying fluid to the emission means. Support means such as a rotary drum is employed in conjunction with the pillow block for moving the film past the pillow block in a substantially contiguous relationship with the emission side of the emission means and in a manner such that the emission means extends across substantially the whole Width of the film. Fluid supply means is associated with the header means for supplying fluid to the emission means with sutficient energy to cause fibrillation or expansion of the film when the fluid impinges thereon.

Accordingly, it is an object of this invention to provide a new and improved method for fibrillating oriented film or for expanding a fibrillated film. It is another object of 3,490,663 Patented Jan. 20, 1970 ice this invention to provide a new and improved apparatus for expanding split film or for fibrillation.

Other aspects, objects, and the several advantages of this invention will be apparent to those skilled in the art from the description, drawings, and appended claims.

In FIGURE 1 there is shown the emission side of a pillow block embodying this invention.

FIGURE 2 shows apparatus employing this invention including the pillow block of FIGURE 1.

FIGURES 36 show a succession of steps efiected by the apparatus of FIGURE 2.

In FIGURE 1 there is shown a pillow block denoted generally as 1 wherein there is an inset fibrillation zone denoted generally as 2. Fibrillation zone 2 is divided into an internal zone 3 and an external zone 4, the two zones being divided by a groove 5 which serves as the fluid emission means for fibrillating the film. On the reverse side of the pillow block as shown in FIGURE 1 and extending therethrough in open communication with the groove 5 is a header means having a plurality of large feed conduits 7 openly connected thereto and a plurality of smaller feed conduits 8 openly connecting the header conduit 6 with groove 5.

The distance W between the bottom two end points of groove 5 is substantially the same as the 'width of the film to be fibrillated, although narrower and wider films can be treated by the same pillow block if desired. In the case of the treatment of a wider film only a portion thereof will be treated and therefore to obtain complete fibrillation the film could be recycled past the same pillow block again so that the untreated portion could then be fibrillated. In the case of a narrower film complete fibrillation thereof will be obtained when the film reaches the point intermediate the upper point 9 and the bottom points 10 and 11 of groove 5.

The film to be fibrillated will first pass into contact with groove 5 at the point 9 at which time only that portion of the film which is exposed to point 9 will be fibrillated, then as the film passes downwardly toward ends 10 and 11 successive areas of the film will be exposed to groove 5 and the fluid emitted therefrom. Thus, succeeding areas across the width and length of the film will be fibrillated until the film passes downwardly from points 10 and 11 at which point it has been completely treated with high energy fluid and therefore very uniformly and completely fibrillated. The localized area of the film exposed to the fluid stream can vary widely in size but its largest diameter or side length will generally be less than 50 percent, preferably 30 percent, still more preferably 10 percent, of the film length or width, whichever is the smaller.

A conventional fluid pumping means (not shown) is connected to large feeder conduits 7 to supply the high energy fluid which is emitted from groove 5.

Conventional sealing means, e.g., a hard rubber flange strip, are applied between the outer edge of groove 5 and zone 4 so that substantial fluid leakage toward the outer edges of pillow block 1 is prevented. Similar conventional sealing means can be employed between the inner edge of groove 5 and zone 3 although this is not necessary since zone 3 is of limited volume and supplemental amounts of fluid can be supplied by the larger feed conduits that are more closely located to the ends points 10 and 11, i.e., in the areas of zone 3 of increasing volume. Thus, supplemental fluid is supplied to the header in the areas where the volume of zone 3 is increasing so that any leakage from groove 5 into zone 3 is compensated for. The bottom conduit 15 is an inlet conduit like conduits 7 whereas 15 is, in effect, an outlet conduit which receives fluid from groove 5 in zone 3 for return to the pumping means and ultimate reuse as a fibrillating fluid.

Fluid flow from zone 3 to zone 4 or vice versa should also be avoided since any substantial amount of this type of fluid flow will cause the film to split excessively or bunch toward the center of zone 3.

Generally, any type of fluid can be employed. Although liquids such as water, or faster drying organic compounds, e.g., acetone, pentane, cyclohexane, and the like, can be employed, air, nitrogen, and similar gaseous materials or mixtures of gaseous and liquid materials can be employed successfully also. The velocity and pressure of the fluid as emitted from groove 5 and impinged on the film to cause fibrillation of same can vary widely depending upon the type of fluid, the composition of film, the degree of orientation of the film, the configuration of groove 5, and various other parameters. Thus, it is virtually impossible to quantify the energy required for the fluid emitted but in all cases the energy will be that which is at least suflicient to cause at least some fibrillation of the film when applied to a small, calized area of that film. The fibrillation fluid can be employed at elevated temperatures or the film to be fibrillated itself can be at an elevated temperature although suitable results are obtained when the process is carried out with the fluid and the film substantially at room temperature. Similarly, temperatures below that of room temperature can be employed if desired. Recycling of the film past the same pillow block can be practiced if a more finely fibrillated product is desired.

The configuration of groove 5 need not be triangular but can vary widely so long as it traverses a width portion of pillow block 1 which is on the order of the width of the film to be fibrillated, the fibrillation fluid thereby gradually coming into contact with substantially the entire width of the film. For example, the high energy fluid stream can be impinged on a first, localized area of the film which first area is between the longitudinal sides (edges) of the film. Thus, the first area can be between and away from either longitudinal side (edge) of the film, and the high energy fluid can then gradually be moved in at least two directions from the first area, the two directions being away from one another and diagonally toward both longitudinal sides of the film. This diagonal movement in at least two directions can be in the form of an isosceles triangle (as shown in FIGURE 1) when the first area of impingement is at a point substan tially centrally located with respect to the width of the film. Both legs 5 of the triangular path of the high energy fluid stream as shown in FIGURE I extend toward a single and the same end of the film, i.e., the end of the film closest to end points 10 and 11 of legs 5. For example, a single diagonal groove can be employed with similar orientation to one leg of groove 5.

The film can be moved through zone 2 at any desired speed, the faster the movement of the film through the zone the coarser the fibrillated product and vice versa. Pillow block 1 can be formed of any conventional material capable of maintaining fluid under pressure which can vary from metals such as steel to polymers such as hard rubber.

Generally any orientable plastic film can be employed in the process and apparatus of this invention. The film will generally be uniaxially oriented although any other condition of orientation which allows fibrillation can also be employed. The film can be oriented in any conventional manner known in the art including super-cooling the film and then orienting same by stretching and the like or heating the film to a temperature below that at which the film is in the molten state and then stretching same. By orientation, what is generally meant to be covered is deforming, e.g., stretching the film below that temperature at which the film is substantially in the molten state, to thereby increase the strength of the film at least in the direction in which it is deformed.

Generally, films of polymers of l-olefins having from 2 to 8 carbon atoms per molecule which have been oriented by stretching in at least one direction so that the film after stretching is at least 3 times longer in the direction of stretching than it was before stretching, i.e., 3 to 1, can be used. When film of polyethylene which has a density of at least 0.94 gram per cubic centimeter is employed the ratio of length in the stretched direction to original length should be at least 4 to 1 and When polypropylene is employed this ratio should be at least 6 to 1. Polymers of l-olefins can be made in any conventional manner. A particularly suitable method is that disclosed in US. Patent 2,853,741. The film can be made from the polymers in any conventional manner such as by extrusion, casting, flattening blown tubing, and the like.

Other conventional plastic films that can be employed in this invention include blends and copolymers of l-olefins as above-described with each other and with other polymers such as polyamides, polyesters, polyvinyl alcohol, acrylic polymers, polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, and the like. Of course, homopolymers of the l-olefins and other materials described can also be employed as well as copolymers. A stretch or orientation ratio of at least 3 to 1 can also be employed with these plastic films.

The film can be of any length and width and substantially any thickness, the minimum thickness of the film being that which will produce a substantially self-sustaining film and the maximum thickness being dictated by the fibrillating capability of the apparatus employed. Generally, the thickness will vary from that which is sufiicient to form a self-sustaining film to about 6 mils. Thicker films can be treated by using fluids of higher energy content or by recycling the film past the same pillow block one or more times. Repeated passes of films past the same pillow block will allow the use of fluid at a lower energy state and still effectively fibrillate thicker and/or tougher films than could be ordinally fibrillated adequately by the lower energy state fluid.

FIGURE 2 shows the pillow block of FIGURE 1 and its relationship with respect to film 20 to be fibrillated and the rotating support drum 21. The film 20 enters the interface between the top drum 21 and pillow block 1 and exits from the bottom of drum 21 as fibrillated product, i.e., non-woven fabric, 22. As the film passes between points 9 and 11 it is fibrillated and the degree of fibrillation at any given point between points 9 and 11 varies increasingly toward point 11. Reference letters A, B, C, and D represent different degrees of fibrillation and are discussed in more detail with reference to FIGURES 3-6. Drum 21 can be any conventional drum made of any conventional material including a steel drum, a rubberfaced steel drum, and the like. The drum is rotated to move film 20 into a contiguous relationship with groove 5 of pillow block 1 and then away from pillow block 1 for subsequent treatment, storage, or other disposal as desired.

FIGURE 3 shows the state of the film in step A. The solid, oriented film is present in inset fibrillation zone 2 of pillow block 1 and carried on the surface of drum 21.

FIGURE 4 (step B) shows header conduit 6 and feeder lines 8 in pillow block 1 feeding high energy fluid to groove 5 and therefore causing fibrillation of the film in a small localized area to produce fibers 30 from that film. Fibers 30 represent the longitudinal stern fibers of a conventional non-woven fabric and the smaller length and diameter cross connecting fibers that are integral with adjacent stem fibers are not shown for the sake of simplicity.

FIGURE 5 (step C) shows substantially the same situation as step B except that the film has traversed further along the length of fibrillation zone 2 so that a large number of successive areas of the film have been subjected to the fibrillation fluid and therefore larger numbers of stem fibers 30 are present, i.e. the film has a larger width thereof fibrillated than step B.

FIGURE 6 (step D) shows the completely fibrillated film as obtained as the non-woven product 22 of FIG- URE 2. When a liquid is used as the fibrillation fluid a conventional drying step is preferred for the product 22. Such drying steps include similarly subjecting the product to a blast of hot, dry air, and the like.

Although the invention has been described relative to fibrillating a film it is equally as applicable to laterally spreading a fibrillated film to make a fabric wherein most all the fibers are sufliciently spaced from adjacent fibers to allow one to see through the fabric, the fibers in the as fibrillated condition being substantially contiguous with adjacent fibers. If the spread fabric tends to return to the closed as fibrillated condition the fluid employed in the process of this invention can contain setting additives or can be heated to thermally fix the fibrillated film in the spread apart (opened out) condition.

EXAMPLE I A film having a 2 mil wall thickness composed of a homopolymer of propylene having a melt flow of 2.5 to 4 (ASTM D123862T, condition L, grams per minutes) and a flexural modulus equal to or greater than 200,000 (ASTM D790-63, 73 F., p.s.i.) is stretched at a temperature of 250 F. until the length in the stretched direction is 7 /2 times that of the original unstretched length. The film is then passed through the apparatus of FIGURE 2 at a rate of about 10 feet per minute and water under pressure of about 2000 p.s.i.g. is fed to header 6. The film and water are substantially at about 75 F.

The product recovered from the bottom of drum 21 is a very uniformly fibrillated non-woven fabric having extremely few and very small areas wherein substantially no fibrillation occurs.

EXAMPLE II The process of Example I is repeated using a film composed of a homopolymer of ethylene having a density of 0.96 gram per cubic centimeter at 25 C. and a melt index of 0.2, and air is the fibrillating fluid.

Polyethylene film is stretched at 240 F. until the stretched length is 6 times that of the original unstretched length. The air supplied to header 6 is under a pressure of about 500 p.s.i.g.

A similar extremely uniformly fibrillated product is obtained.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope thereof.

Processes similar to those of Examples I and II are repeated on the fibrillated films of those examples and an opened-up nonwoven fabric obtained.

I claim:

1. An apparatus for fibrillating an oriented plastic film comprising: a pillow block having a groove formed therein, said groove being configurated to provide elongate portions having their inner ends interconnected and extending divergingly from said interconnected ends and terminating at outer ends in spaced relation equal substantially to the width of said film; header means operatively attached to said groove for supplying fluid to said groove; means for moving said film past said pillow block in a substantially contiguous relation with said groove and in registry therewith so that said groove extends across at least a part of the width of said film; and means for supplying fluid to said header means.

2. The apparatus according to claim 1 wherein said groove is in the form of an inverted V, the width between the bottom points at the V of said inverted V being substantially the width of the film to be treated.

3. Apparaus comprising a pillow block having a groove formed therein, said groove extending diagonally across at least part of the width thereof, the width of the portion of said pillow block that contains said diagonal groove being in the order of the width of the film to be treated, header means operatively attached to said groove in at least one place for supplying fluid to said groove, means for moving a film past said pillow block in a substantially contiguous relation with said groove and in registry therewith so that said groove extends across at least part of the width of said film, and means for supplying fluid to said header means.

4. The apparatus comprising a pillow block having a hemispherical depression therein and said hemispherical depression contains an inset zone which is narrower at the top than the bottom thereof, said inset Zone containing a groove means in the form of an inverted V so that the apex is in the top, narrow portion of said inset zone; header means for supplying fluid to said groove, said header means including a header conduit in said pillow block adjacent the curved face of said hemispherical depression which follows the curvature of that face, said header conduit having a plurality of smaller feeder conduits openly connected to said inverted V groove at a plurality of points intermediate the apex of said groove and the bottom two points of said groove, and a plurality of larger feeder conduits operatively connected to said header conduit along the length thereof, a pump means and fluid source operatively connected to said larger diameter feeder conduits; and means for moving the oriented filrn past said pillow block, said means including a rotatable drum means extending partially into said hemispherical depression, the diameter of said drum means being slightly less than the diameter of said hemispherical depression.

References Cited UNITED STATES PATENTS 3,177,557 4/1965 White 22593 X 3,293,844 12/1966 Wininger et al 22593 X JAMES M. MEISTER, Primary Examiner US. Cl. X.R.

Disclaimer and Dedication 3,490,663.Bradley Skinner, Bartlesville, Okla. FIBRILLATION. Patent dated J an. 20, 1970. Disclaimer and dedication filed Dec. 28, 1971, by the assignee, Phillips Petroleum Company. Hereby disclaims said patent and dedicates to the Public the ren'laining term of said patent.

[Ofiicz'al Gazette April 11, 1972.] 

